a) Field of the Invention
The present invention relates to a windshield wiper blade, and more particularly, to a wiper blade with spoiler.
b) Description of the Prior Art
Currently, windshield wiper assemblies of many different types are available but also it is well known that they have a tendency to lift from the window pane being cleaned when the vehicular driving speeds are high. For solving this problem, wiper blade assemblies with a spoiler have been proposed. For instance, the U.S. Pat. No. 4,741,071 discloses a windshield wiper blade assembly of which the main yoke has a spoiler formed integrally therewith. The spoiler extends from the rim of one of the side walls of the main yoke adjacent to the wiper element. In this known wiper blade assembly, the width and height of the side walls are selected such that the effective angle for the air stream between an imaginary line connecting the upper edge of the side wall and the free rim of the spoiler lies between 30 degrees and 60 degrees. To solve the same problem as discussed above, another solution has been proposed in the Japanese Unexamined Utility Model Publication No. 55-65244 which discloses a windshield wiper blade assembly having a spoiler formed separately from the main yoke thereof. FIG. 1 schematically shows a conventional wiper blade assembly of this kind. As seen, a vertebra 1 supporting a blade rubber 2 which is used to wipe a window pane 8 is supported by a primary yoke 5 by means of clawed yokes 3 and secondary yokes 4. The primary yoke 5 is supported by a wiper arm mounted on a wiper drive shaft (both not shown) and it is so driven, by a reciprocal circular motion of the wiper arm, as to make a reciprocal circular motion about the wiper drive shaft as indicated by the arrows a and b. In FIG. 1, the arrow A indicates a direction toward the wiper drive shaft, while the arrow B indicates a direction of the wiper blade motion away from the wiper drive shaft. A spoiler 6 is fixed to this primary yoke 5 and the angle of inclination thereof with respect to the window pane 8 is so selected that the air blown to the blade and spoiler 6 in the direction of arrow c along the window pane 8 is deflected in the direction of arrow d to produce in the direction of arrow Pl a force which presses the wiper blade to the window pane 8. The force in the direction of arrow Pl is conveniently increased or decreased as the vehicular driving speed is increased or decreased.
In the wiper blade assembly with the above-mentioned spoiler, however, the air stream flows into the back of the spoiler at one end of thereof which is nearer to the wiper drive shaft, and the air stream impinging on the spoiler front surface also enters the back of the spoiler at the other end thereof which is farther from the wiper drive shaft. These problems remain unsolved in the conventional wiper blade assemblies art. This will be further described below.
Since the wiper blade is reciprocally oscillated about the wiper drive shaft in the directions of arrows a and b, the position and angle of inclination thereof incessantly vary while in use. However, as the end of the spoiler at the wiper drive shaft side is almost always lower than the rest of the spoiler, it is likely to be affected by the wind or air stream impinging upon the hood of the car and flowing up in the direction of arrow e along the window pane. A part of the wind flowing in the direction of arrow e flows in between the spoiler 6 and blade rubber 2 as indicated with the arrow h and acts to force up the spoiler 6 from inside thereof, thus further causing the blade rubber 2 to lift from the window pane. This is the problem of "air stream flow-in" at the one end of the spoiler nearer to the wiper drive shaft.
Also, in the proximity of the other end of the spoiler 6 opposite to the wiper drive shaft, the wind blown in the direction of arrow i is deflected longitudinally of the spoiler 6 as indicated with the arrow j. The wind or air stream in this direction of arrow j is not sufficiently effective in forcing the wiper blade to the window pane 8. Furthermore, a part of this wind in the direction of arrow j flows into the back of the spoiler 6 as indicated with the arrow k and forces up the spoiler 6 from inside thereof. Namely, the air stream acts to further the lifting of the blade rubber 2.
These problems are found also in the wiper blade assembly disclosed in the previously-described U.S. Pat. No. 4,741,071.